The dramatic helicopter departure from a Pakistani jail of a Christian girl accused of blasphemy was more than a cinematic denouement. It marked a watershed moment for Pakistan, which has a long history of ignoring the persecution of accused blasphemers rather than rescuing them.

There has been nothing like this in Pakistan's history. One of the girl's lawyers, Tahir Naveed Chaudhry, said it was the first time anyone had ever been released on bail after a blasphemy arrest.

Flanked by heavily armed guards, the girl was escorted to a waiting government helicopter and flown from the high-security jail in Rawalpindi where she had been held for three weeks after a mob threatened to set her on fire for allegedly desecrating the Qur'an.

The head of Ulema Council, a clerical group, said the granting of the Christian girl's release on $10,500 bail was a "victory for justice".

Despite the controversy surrounding the blasphemy laws, government officials had been reluctant to speak out against them. But the Christian girl's case sparked an international wave of support, and inside Pakistan itself, Muslims and minorities alike rallied to her defence. The girl's age, the thinness of the evidence against her, and reports that she has a mental disability may have all helped in galvanising public support.

The numbers in a report by the Islamabad-based Centre for Research and Security Studies (CRSS) tell a stark story of what critics see as a shameful abuse of the blasphemy law, which makes it a crime punishable by death or life in prison to defame Islam's prophet or desecrate the Qur'an.

Under British rule, from 1851 to 1947, there were only seven blasphemy related incidents, the study said. But during the 1977-1988 military rule of Zia ul-Haq – the military dictator credited with Islamicising Pakistan – as many as 80 blasphemy cases were taken to court. Since then, nearly 250 blasphemy cases have been lodged.

The report tallied those accused of blasphemy over the decades, from 1953 to July 2012. Of the 434 offenders 258 were Muslims, 114 Christians, 57 Ahmadi (a minority sect that the Pakistani constitution has declared non-Muslim) and four Hindu.

Since 1990, the report said, 52 people have been extra-judicially killed, for being implicated in blasphemy charges. Half were Muslim, 15 Christian, and the rest from different minority religions.

Pakistani President Asif Ali Zardari himself took "serious note" of the young Christian girl's arrest and said: "Blasphemy by anyone cannot be condoned but no one will be allowed to use blasphemy law for settling personal scores." He also ordered the interior minister to investigate the case.

Interior minister Rehman Malik all but pronounced the girl innocent, saying the accused never left her home on the day when a young man claimed to see her carrying burnt pages of the Qur'an in a trash bag in her village in the suburbs of Islamabad.

The concern displayed by the ruling party may also be unprecedented. "The PPP is the only political party to support religious freedom of minorities," said Paul Bhatti, who heads the ministry for national harmony, a position created after his younger brother, Shahbaz Bhatti, the minority affairs minister, was assassinated in 2011 for speaking out against the blasphemy laws. Another prominent politician, Salman Taseer, was killed earlier that same year for expressing support of an accused blasphemer.

Xavier William, president of the non-denominational non-profit Life for All in Pakistan, sees the politicians' declarations as a good sign. "They show that they are open to amending these laws so they cannot be misused," he said. "It's time to act for them. They have already lost two of their ministers to this cause but now with the president's statement we are hopeful."

Allama Yasir Abbasi, an imam at a mosque in Islamabad, summed up the balance that religious leaders face given the supreme importance of respecting the Qur'an and the prophet Muhammad. "If Christians complain that they are discriminated against, those complaints should be looked into," he said. "But at the same time, the followers of other religions must also respect Islam the way we respect other religions."